BAGHDAD, Iraq - A suicide car bomber and gunmen ambushed a convoy carrying female U.S. Marines in Fallujah, killing two Marines and leaving another four American troops presumed dead, the military said Friday. At least one woman was killed and 11 of 13 wounded were female.

The terror group al-Qaida in Iraq claimed it carried out the bombing, one of the single deadliest attacks against the Marines - and against women - in this country. The high number of female casualties spoke to the lack of any real front lines in Iraq, where U.S. troops are battling a raging insurgency and American women soldiers have taken part in more close-quarters combat than in any previous military conflict.

The women were part of a team of Marines who were assigned to various checkpoints around Fallujah. Female Marines are used at the checkpoints to search Muslim women "in order to be respectful of Iraqi cultural sensitivities," a military statement said. It is considered insulting for a male Marine to search a female Muslim.

Current Pentagon policy prohibits women from serving in front line combat roles - in the infantry, armor or artillery, for example.

"It's hard to stop suicide bombers, and it's hard to stop these people that in many cases are being smuggled into Iraq from outside Iraq," President Bush said at a joint White House news conference with Iraqi Prime Minister Ibrahim al-Jaafari.

The Marines were returning to their base, Camp Fallujah, when the ambush took place Thursday night near the eastern entrance to the city, 40 miles west of Baghdad.

Fallujah is a former insurgents' fortress that was invaded by U.S. forces at great cost last November; it also the city where an Iraqi mob hung the mutilated bodies of two U.S. contractors from a bridge. On Nov. 2, 2003, two female Army soldiers were in a Chinook helicopter shot down over Fallujah.

At least one of the dead Marines in Thursday's attack was a woman, as were 11 of the 13 wounded.

The male Marine was killed by small arms fire immediately afterward, the military said. His family identified him as Cpl. Chad Powell, 22, from northern Louisiana. Powell is survived by his parents, his wife and a 3-year-old son, Elijah.

The military did not provide the genders of the missing three Marines and a sailor who were believed to be in the vehicle that was attacked. They were presumed dead, said a U.S. military official in Washington who spoke on condition of anonymity because the victims have not been identified.

Thirty-six female troops have died since the war began, including the one that was announced Friday, said Maj. Michael Shavers, a Pentagon spokesman. Thirty-four were Army, one Navy and one Marine.

With Thursday's suicide attack, the death toll among U.S. military members since the beginning of the war reached 1,732. It came as Americans have grown increasingly concerned about a conflict that has shown no signs of abating. One year ago, 842 U.S. service members had died in Iraq, compared to 194 on that date in 2003.

The relentless carnage has killed more than 1,240 people since April 28, when al-Jaafari announced his Shiite-dominated government. With the Sunni Arab-dominated insurgency targeting the Shiite majority, the wave of killings has slowly been pushing the country toward civil war.

In one such sectarian killing, gunmen on Friday killed an aide to Grand Ayatollah Ali al-Sistani, Iraq's most revered Shiite cleric. Police said two bodyguards were also killed trying to protect Shiite cleric Samara al-Baghdadi, who represented al-Sistani in Baghdad's predominantly Shiite al-Amin district.

Iraqi security forces also discovered the bodies of eight beheaded men - at least six of whom were Shiite farmers - in a region north of Baghdad on Friday. It was unclear why the men were killed.

News of the Marine deaths came as Bush and al-Jaafari both pledged eventual victory over insurgents.

"The enemy's goal is to drive us out of Iraq before the Iraqis have established a secure democratic government. They will not succeed," Bush said.

Fallujah, in Anbar province, was the scene of a large-scale campaign in November by U.S. troops to rout militants.

Residents of Fallujah call it the "City of Mosques" for its many Muslim houses of worship. Along with neighboring Ramadi, the city and the region around Fallujah are located in the heart of the insurgency that is fighting both the U.S. military presence in Iraq and al-Jaafari's government

Things came to a head In Fallujah in March 2004 with the grisly killings of four U.S. contractors whose bodies were mutilated, including the two hung from the bridge. That prompted a siege by Marines and heavy fighting.

A U.S.-led offensive in November finally wrested Fallujah from insurgents. The U.S. military says 1,200 insurgents were slain and about 2,000 suspects captured in the battle. At least 54 U.S. troops and eight Iraqi soldiers were killed.

The State Department says about 90,000 of Fallujah's 300,000 residents have recently returned to the city, which benefited from Saddam Hussein's 23 years in power, as did other cities in the Sunni-dominated area north and west of Baghdad. The former dictator, himself a Sunni, recruited many Republican Guard officers and security agents from the area.

U.S. forces in Fallujah arrested Associated Press Television News cameraman Amer Ali who went to the scene of the ambush at midday Friday, and his video showed black scorch marks along a road and scattered chunks of metal. Video shot Thursday showed thick plumes of black smoke rising from the blast.

Since the November offensive, the Marines have been involved in numerous operations to root out insurgents in western Anbar, including a recent campaign near the Syrian border that killed 47 insurgents.

On June 19, Marines from the 2nd Marine Division fought a fierce battle with two groups of insurgents and a suicide car bomber just outside Fallujah. At least 15 insurgents were killed. No Marines were injured.

In other violence Friday:

- An Iraqi reporter working for an American news organization was shot and killed in Baghdad by U.S. troops after he apparently did not respond to a shouted signal from a military convoy, witnesses said. The military had no comment.

- Gunmen killed police Lt. Col. Majid Faisl Aziz when he was driving his car near western Baghdad's Amiriyah neighborhood, police Capt. Talib Thamer said. Aziz was a member of the Interior Ministry's major crimes division.

- A Kurdish contractor working for the American military was killed by gunmen in northern Kirkuk.

- In Baghdad, three police officers were killed in separate incidents, two in the Amiriyah district and another in southern Dora, police and hospital officials said.